Test Equipment Anonymous (TEA) group therapy thread

[tggzzz]

It amazes me how youtube is a pile of shit and a goldmine at the same time.

This seem to validate Sturgeon's hypothesis, I think the ratio is accurate as well.

Sturgeon was an optimist.

[TERRA Operative]

Vince what is your opinion ...

If we want to replace a knob or button on our vintage instrument, does the button need to look brand new, or does it need to look like other buttons that are "weathered" (model RR term) and used? Which is the perfect choice in your opinion?

 

Gotta replace them all to keep it all a matching set! 

Or just repair the knob with J-B Weld. 

[DH7DN]

Vince what is your opinion ...

If we want to replace a knob or button on our vintage instrument, does the button need to look brand new, or does it need to look like other buttons that are "weathered" (model RR term) and used? Which is the perfect choice in your opinion?

 

Gotta replace them all to keep it all a matching set! 

Or just repair the knob with J-B Weld. 

Beautiful repair, I liked that video 

[VK5RC]

Here is the final Boonton button finishing test.

The finished 3D (meaning additional finishing after the print) printed button is on the left, original right. The last pic has the finished button left, original Boonton button middle, unfinished (except for the dot) 3D printed button at the right. The finishing of the 3D printed button involved sanding and priming (3 times), then final painting with Tamiya X-1 black gloss model paint. The white dot was applied with a toothpick using Tamiya XF-2 flat white.

Honestly, when I set up the two buttons for pics I left the room to do some things. When I came back I forgot how I set them up. I could not tell which was which until I got up very close. I do not think a person without prior knowledge would be able to distinguish the finished button from the originals when all are installed and the bezel in place - especially if they didn't even know a button had been replaced.

Heck, even if you don't want to go to all the trouble I did, just a few quick touches with a very fine sandpaper on all sides & painting once would make a great improvement.

So I hope this shows that you can do a whole lot more to the 3D printed object after it is removed from the printer, especially if you want a "museum quality" replacement part.

Really great result
Can I be obsessive?
How fine was the sandpaper - I would guess something like 400?
The primer - was it also a Tamiya? I imagine their paints are great at holding onto plastic.
Also - this was brushed not spray painted (air brushed) ?
(thinking of an entry in the repair - classic etc list) 👍
Thanks for sharing
Rob

[VK5RC]

A bit off topic but fits the repair theme.
My wife decided to see if she could fly down the stairs - gravity won - her ankle lost. Fractures on both sides of the ankle and dislocated about 1-2 inches!
She now has a bionic foot! Well nearly - but the orthopaedic surgeon is happy with the result - looks good 👍

[Neper]

I've had that exact failure too. On same  model car.

The thermostat appears to be a general Volvo prob. I've had it on the 121, 144, 244, two 264 and a 760. All of them bought second-hand, all of them with broken thermostat that wouldn't close anymore. Engine wouldn't reach normal temperature, no decent heating (in a Volvo!).

[ch_scr]

Today I got a package from Mounty, seems he decided it's already christmas day again 
From the packaging alone, some sellers could learn something...

Inside, even more packaging, to protect the goodness...
And I'm greeted by some 3M "Safety diskettes" post-it note blocks
"One less worry" indeed, I'll be sure to recommend them 

After unwrapping, here is what we see:

2x CTI OCXO, more on them later
2x 6Н21Б miniature tubes, true marvels of (soviet) engineering..
(6V indirect heated, 200V / 1W anode, gain of up to 100, double triodes)
...all in the size of a child's pinkie!
3x S20K250 varistors for protection 
2x Capacitor & discharge resistor assemblies, with military markings.
(DE5000 indicates these are spot-on at 100Hz, whilst beeing older than I am)
1x bag of pure analog goodness, consisting of:

2x LM224 CerDip Quad opamp
4x MC3403 Quad opamp
3x LF355 Fet Input fast opamp
5x UA709 these are "red dot special" adventurous type opamp
1x AD584 pin-programmable reference (1.21 to 10V)
1x LM358 Opamp in metal can
and, star of the show (drumroll . . . )
3x 2DW23x ultra-low-noise dual zener diodes from "Shanghai 17th Radio Factory"
in different "Zero TC" current ratings, marked by label and color dot.

AMAZING!

Many thanks Mounty! I could not stop smiling whilst writing this
Now, biggest problem is not to get distracted from project at hand 

[McBryce]

I also have serious doubts abut relying on regenerative braking will be sufficient because it relies on having a load connected to the motor to generate that braking effect, now what would happen if by any chance that load were to be disconnected, due to a number of possibilities, loose connection, fractured connection etc, all braking would be lost.  For that reason, I think that disc brakes would still be required, but they would in effect be used in the main for emergency braking and also for the final coming to a rest where you require being rather than where the car and other external forces such as a nudge from another vehicle, gravity, wind etc decide where you're going to actually stop.

My current ICE car has regenerative braking on it, and while it's not aggressive, it is noticeable, and I can in many instances rely on it to drop my speed, if I'm given plenty of time to react correctly, it cannot bring me to a complete standstill, I still require brakes for that last bit. But in reality that does not happen very often as you simply are not given that luxury of having the road to yourself. There is always going to be interplay with others, be it in the form of pedestrians, animals, other road users etc to prevent the effective use of regenerative braking alone.

Being able to brake is a serious issue with all kinds of vehicles. So for any reasonable safety assesment, you'd need a redundant way to brake, as regenerative and active braking can't fulfil this safety requirement in a reasonable way. Ask me how I know (disclaimer: I never worked for automotive, but for industrial drives, and made a safety assessment for "motor braking" in robotic applications). It's quite difficult to fulfll safety requirements for safe braking considering all the faults an electrical system can have. So you'd always want a secondary (mechanical) brake that is able to stop the vehicle at an emergency situation.

Next issue is maximum braking deceleration. Synchronous motor mechanical torque is proportional to motor current at the electrical side, completely independent of rotational speed and direction. For economical reasons there's an upper limit for the motor current, set by inverter and motor design. You'd set this limit to your wanted acceleration performance of the car. For emergency braking, you'd want a significantly higher torque limit, that would at least require a more expensive inverter design (as in larger IGBTs) and most probably additional resistors to dissipate the braking energy as the battery has a max. charging current limit, too. In total, this most probably would be more expensive than just the additional mechanical brakes.

And yes, of course, technically the inverter can decelarate and "hold" the motor at zero rpm infinitely at nominal torque (equal to max. acceleration torque). But this would require measures to cope with constantly high current, accelerating is "pulse load" at least for the thermal mass of the motor components (to to the inverter, the typical IGBTs thermal mass is just good for some µs to ms ballpark values).

All that, plus the fact that regen braking stops working if the power source is removed, so the safety guys will never accept a system that doesn't work on pure mechanics (at least in the automotive world).

McBryce.

Not true. You don't need a power source to get regenerative braking. By definition it is producing electrical power not using it. Get a DC motor and try spinning the shaft. Then short the windings and try spinning it again. That resistance is dynamic breaking. Of course, as discussed earlier it does not work if the motor is not turning so is innefective when stationary or at low speeds. That is when DC injection braking is needed. Injection braking does of course consume power. This defeats the object so you still need friction brakes or a transmission lock.

Yes, but that's not how it works in real vehicles. Of course shorting a DC motor blocks the shaft (in a lab), but vehicles use 3 phase AC motors and blocking the motor without being able to control the amount of braking, switching the supply source in an emergency situation etc would just never be allowed. By the time you added additional battery backed regulation (for voltage coming from the motors) plus additional control circuitry that would have to be always active, you'd have a system that was heavier, more expensive and less reliable than simply leaving mechanical brakes as a backup and it still would only work if you added a massive dummy load in case the HV battery was fully charged at the time.

McBryce.

[mansaxel]

It's the river Cam but not much better than a canal. Orli is no longer with us but she hated water. She tried one paw off the punt and withdrew quickly. She loved going out on a punt. She certainly surprised a few foreign tourists who started taking photos of her instead of the colleges.

Cam is joined by a bunch of canals, IIRC. Reason canals are worse is of course that the CRT or Wasseramt or whoever are managing the canal does not want flow, because flow equals cost. Canals that are anything else than "simple" single-pond structures like the Suez canal need to be refilled because locking taps them, and this is one of the the largest headaches in all waterworks civil engineering. The Canal du Midi was not begun before Riquet found a way to replenish it, using water from as far away as 50km.

[capt bullshot]

The emergency fault problems you've described are just the tip of the iceberg for "one motor per wheel" designs in real life. At low speeds things generally behave... but at anything approaching highway speeds, this will require real-time active mixing of the motor ESCs similar to that used in a flight controller.

This is something I have first-hand experience with trying to build large-scale AWD stadium trucks. ...

I have no experience with per wheel direct drive motor designs in vehicles. And I can't help with mass placement optimizing and so on. Anyway, I do know what modern industrial motor controllers can do, and that's way above what your flight controller in a drone can do, or in any (larger or smaller) model does. Electronic gearboxes are just one of the rather well-known and simple applications. So real time emulating the behaviour of a 2WD differential, or multiple differential (and locked) 4WD is nowadays nothing too exciting for these controllers. The system should also be able to actively steer the "emulated" mechanical differentials in more ways than the mechanical ones, intended as driver assistance. It's perfectly possible, but a big heap of work for the engineers to correctly design and validate this so the vehicle doesn't behave unexpectedly.

[BU508A]

Today I got a package from Mounty, seems he decided it's already christmas day again 
From the packaging alone, some sellers could learn something...

Inside, even more packaging, to protect the goodness...
And I'm greeted by some 3M "Safety diskettes" post-it note blocks
"One less worry" indeed, I'll be sure to recommend them 

After unwrapping, here is what we see:

2x CTI OCXO, more on them later
2x 6Н21Б miniature tubes, true marvels of (soviet) engineering..
(6V indirect heated, 200V / 1W anode, gain of up to 100, double triodes)
...all in the size of a child's pinkie!
3x S20K250 varistors for protection 
2x Capacitor & discharge resistor assemblies, with military markings.
(DE5000 indicates these are spot-on at 100Hz, whilst beeing older than I am)
1x bag of pure analog goodness, consisting of:

2x LM224 CerDip Quad opamp
4x MC3403 Quad opamp
3x LF355 Fet Input fast opamp
5x UA709 these are "red dot special" adventurous type opamp
1x AD584 pin-programmable reference (1.21 to 10V)
1x LM358 Opamp in metal can
and, star of the show (drumroll . . . )
3x 2DW23x ultra-low-noise dual zener diodes from "Shanghai 17th Radio Factory"
in different "Zero TC" current ratings, marked by label and color dot.

AMAZING!

Many thanks Mounty! I could not stop smiling whilst writing this
Now, biggest problem is not to get distracted from project at hand 

You are welcome! 
The 3M sticking notes, the LM224, MC3403 and LF355 have been sent to me as a surprisiung gift as well!
Since I've got so much of them, I decided to share some of them. Glad, that you've enjoyed it. 

The UA709, the varistors and the military capacitors are genuine Rohde & Schwarz spare parts.

I wish you a lot of fun with your new toys.
Sadly, the parcel took so long to you, I thought really, you should have it latest on Friday.

[Specmaster]

and there is similar carnage in the guest bedroom...

alt-codes work here: alt-225 = ß    alt-230 = µ   alt-234 = Ω   alt-236 = ∞   alt-248 = °   alt-0216 = Ø

With a Real Computer (or as close as we people who still have Intel CPU's in our macs can manage) and a proper keymap, Alt-codes are not necessary.

ß µ Ω ∞ ° Ø

Technically, you of course still need to press "alt", but there is no code typing, it's, on this mapping,

s, y, w, 5, shift+the-button-left-of-1-which-is-marked-§-and-°, and, le grande Finale: shift-ö. Because ø is ö in Denmark and Norway, so a Scandinavian keyboard needs it, in the Nordic brotherhood tradition.

Historical tidbit: In the late 1940's, there was some effort in getting a defense alliance going in the Nordics. It was given up, partially because Finland could not be in -- they'd lost the war by being beaten by the Soviets, and were held to a "Peace and Friendship agreement" made up by Stalin and Molotov, so could not take part -- but more so by Norway and Denmark trusting the USA / UK team a bit more. We're still friends, and we don't need passports, even if Norway is not in the EU.

Finland were, in the early 90s, quick to notice that as the Soviet Union had ceased to exist, the agreement could not possibly be valid, and declared themselves unbound by it, which was followed by a new agreement with Russia.

Fair enuf, but I was mostly just trying to help most users get a usable ° and a Ω that doesn't look like blurry ass. 

mnem
*toddles off to ded*

Mmm.. your codes
alt-225 = ß    alt-230 = µ   alt-234 = Ω   alt-236 = ∞   alt-248 = °   alt-0216 = Ø don't work that way on my setup  , I get
alt-225 = ß    alt-230 = µ   alt-234 = Û   alt-236 = ý    alt-248 = °   alt-0216 = Ø   

[BU508A]

Mmm.. your codes
alt-225 = ß    alt-230 = µ   alt-234 = Ω   alt-236 = ∞   alt-248 = °   alt-0216 = Ø don't work that way on my setup  , I get
alt-225 = ß    alt-230 = µ   alt-234 = Û   alt-236 = ý    alt-248 = °   alt-0216 = Ø   

Extended ASCII table from the Microsoft developers blog:



Not sure, why you are getting different results.
Sometimes, a little trick helps: try a leading zero. alt-0236 instead of alt-236.

[Martin Miranda]

hitachi 60mhz probe. (my first ever oscilloscope probe that i acquired), sitting in the junk pile.
- i just washed the variable cap with alcohol. 

[Specmaster]

Mmm.. your codes
alt-225 = ß    alt-230 = µ   alt-234 = Ω   alt-236 = ∞   alt-248 = °   alt-0216 = Ø don't work that way on my setup  , I get
alt-225 = ß    alt-230 = µ   alt-234 = Û   alt-236 = ý    alt-248 = °   alt-0216 = Ø   

Extended ASCII table from the Microsoft developers blog:



Not sure, why you are getting different results.
Sometimes, a little trick helps: try a leading zero. alt-0236 instead of alt-236.

Nope, I then get completely differant results eg.

alt-234 = Ω   alt-236 = ∞
alt-234 = Û   alt-236 = ý
alt-0234 =ê   alt-0236 = ì

EDIT
Looking at the extended ASCII table I seem to getting
alt-0234 =ê (alt-136)  alt-0236 = ì (alt-141)

[Cerebus]

Beautiful creature, when I had a dog, there is no way on earth that she would have been in a punt, she would have been in the river, she really was a dog fish.

That looks like a canal. And while "wet dog" smells horrible, "wet dog from bathing in the canal" has all chances of smelling worse than horrible. For staying dry, I say "Good dog!".

It's the river Cam but not much better than a canal. Orli is no longer with us but she hated water. She tried one paw off the punt and withdrew quickly. She loved going out on a punt. She certainly surprised a few foreign tourists who started taking photos of her instead of the colleges.

In the early 80s I used to go kayaking in the Cam upstream of Cambridge.

Nice and peaceful, with one surprising benefit: after upending myself, my hayfever disappeared for a week.

Probably kept your immune system busy enough with real work that it didn't have time to respond to false alarms for a week. 

I don't make a fuss about it* but I'm plagued by allergies. One of the oddly pleasant side effects of getting a cold, or a fresh vigorous new vaccination, is that I enjoy a few allergy free days. It seems like one's immune system has a limited capacity under "business as usual" circumstances and mild infections (or pseudo infections) use that up capacity leaving little free for minor allergic reactions.

*Unlike a certain class of people who invent allergies and intolerances for themselves, usually after reading an article in some periodical that is better used for personal hygiene of a bottom related nature. It's effing annoying to sit in a restaurant and listen to some muppet who's "avoiding gluten dh-arling" while you've got an Epipen in your pocket becuase you're eating somewhere where you don't have accurate control over the ingredients you're eating.

[Cerebus]

Reason canals are worse is of course that the CRT or Wasseramt or whoever are managing the canal ...

"British Waterways Board" as was, then "British Waterways", now the "Canal & River Trust".

[mansaxel]

Sometimes, a little trick helps: try a leading zero. alt-0236 instead of alt-236.

Character sets are a mess. Through and through. That's why.

The only one that's reasonably sensible is UTF-8, because it encodes the entire Unicode space. All those intermediates that were invented to stick a nationalistic subset of characters into 7 or 8 bits just made matters worse.  It does not matter whether it's Koi-8r, Latrine-[[:digit:]], ISO-646-SE, Mac-Roman or Windows-1252. They all suck.

Make your information processing systems UTF-8 and win.

[m k]

He then checked the cooling circuit for proper operation, gave me the phone call and charged me 260€.

And now everything is cool again and you've learned to follow the gauge?

It used to be so that old thermostat took some time to open and old non damped meter ratted it out.

[BU508A]

Sometimes, a little trick helps: try a leading zero. alt-0236 instead of alt-236.

Character sets are a mess. Through and through. That's why.

The only one that's reasonably sensible is UTF-8, because it encodes the entire Unicode space. All those intermediates that were invented to stick a nationalistic subset of characters into 7 or 8 bits just made matters worse.  It does not matter whether it's Koi-8r, Latrine-[[:digit:]], ISO-646-SE, Mac-Roman or Windows-1252. They all suck.

Make your information processing systems UTF-8 and win.

Amen to that.

[mnementh]

It amazes me how youtube is a pile of shit and a goldmine at the same time.

There's some poetry in that there statement... 

mnem

[vk6zgo]

Sort of reminds you of Y2K, don't it? That turned out to be a little mouse fart into a hurricane. 

Simply because the scare was large enough. A lot of people worked long hours to find and fix problems, and because they did, and because even the very definition of dim-wit, the MBA turned manager, realised there was significant risk in deferring the problem to reactive rather than proactive, there was enough push in the industry to fix the problems in time.

I declare Y2K a success, not a "mouse fart into a hurricane", because that is how good engineering in computing looks. It simply works.

There was, however, a lot of nonsense about aircraft falling out of the sky & the Electricity grid crashing.
Lay people /journalists were not aware that industrial stuff normally operates on "elapsed time", not calendar time.

[mnementh]

Just ordered:
1 Set of original GenRad GR900 adaptors.
(GR900<>N-f, GR900<>N-m, GR900<>BNC-m, GR900 50R Termination)

Wow, those are not very common. What's your use case?

Actually, besides BU508s post MAYBE having a grain of truth(*), the best of my sliding tuner stubs is fitted with this connector.

Besides this, I saw it used on a large step attenuator and a special antenna for EMP testing, which I do not own.
That antenna was very interesting. It was a parabolic reflector fed from behind, with the feed line connected to multiple points and actually being a short at DC. That's all I can recall, as I was discouraged from looking longer and I was not given it's exact purpose.
So, I do have an application and I have seen them in application, which is more than I can say about the last-aquired 'WECO' adaptors, which are therefore more exotic to me.
Of course, I would not be averse to aquire this slotted line: https://www.pa4tim.nl/?p=4978
And OH WEY! the 101 page document collection from GenRad about this connector seems to hint at RF connectors previously unknown to me!

For those not having seen or heard of this connector before: It was GenRad's bet to make a connector in the same class as subsequently fulfilled by the APC-7, although limited to 8.5GHz.

*: of course, this is an entirely uncalled-for wording for 'hoping to aquire any type of RF adaptor before I need it'.

BTW: Interesting website/company for the antipodean fellows: https://halberdbastion.com/

I love the smell of shameless RF Nerdity in the mornin'; smells like... propagation! 

mnem

[mnementh]

It amazes me how youtube is a pile of shit and a goldmine at the same time.

This seem to validate Sturgeon's hypothesis, I think the ratio is accurate as well.

Sturgeon was an optimist.

So was Murphy.

mnem
 

[Robert763]

I also have serious doubts abut relying on regenerative braking will be sufficient because it relies on having a load connected to the motor to generate that braking effect, now what would happen if by any chance that load were to be disconnected, due to a number of possibilities, loose connection, fractured connection etc, all braking would be lost.  For that reason, I think that disc brakes would still be required, but they would in effect be used in the main for emergency braking and also for the final coming to a rest where you require being rather than where the car and other external forces such as a nudge from another vehicle, gravity, wind etc decide where you're going to actually stop.

My current ICE car has regenerative braking on it, and while it's not aggressive, it is noticeable, and I can in many instances rely on it to drop my speed, if I'm given plenty of time to react correctly, it cannot bring me to a complete standstill, I still require brakes for that last bit. But in reality that does not happen very often as you simply are not given that luxury of having the road to yourself. There is always going to be interplay with others, be it in the form of pedestrians, animals, other road users etc to prevent the effective use of regenerative braking alone.

Being able to brake is a serious issue with all kinds of vehicles. So for any reasonable safety assesment, you'd need a redundant way to brake, as regenerative and active braking can't fulfil this safety requirement in a reasonable way. Ask me how I know (disclaimer: I never worked for automotive, but for industrial drives, and made a safety assessment for "motor braking" in robotic applications). It's quite difficult to fulfll safety requirements for safe braking considering all the faults an electrical system can have. So you'd always want a secondary (mechanical) brake that is able to stop the vehicle at an emergency situation.

Next issue is maximum braking deceleration. Synchronous motor mechanical torque is proportional to motor current at the electrical side, completely independent of rotational speed and direction. For economical reasons there's an upper limit for the motor current, set by inverter and motor design. You'd set this limit to your wanted acceleration performance of the car. For emergency braking, you'd want a significantly higher torque limit, that would at least require a more expensive inverter design (as in larger IGBTs) and most probably additional resistors to dissipate the braking energy as the battery has a max. charging current limit, too. In total, this most probably would be more expensive than just the additional mechanical brakes.

And yes, of course, technically the inverter can decelarate and "hold" the motor at zero rpm infinitely at nominal torque (equal to max. acceleration torque). But this would require measures to cope with constantly high current, accelerating is "pulse load" at least for the thermal mass of the motor components (to to the inverter, the typical IGBTs thermal mass is just good for some µs to ms ballpark values).

All that, plus the fact that regen braking stops working if the power source is removed, so the safety guys will never accept a system that doesn't work on pure mechanics (at least in the automotive world).

McBryce.

Not true. You don't need a power source to get regenerative braking. By definition it is producing electrical power not using it. Get a DC motor and try spinning the shaft. Then short the windings and try spinning it again. That resistance is dynamic breaking. Of course, as discussed earlier it does not work if the motor is not turning so is innefective when stationary or at low speeds. That is when DC injection braking is needed. Injection braking does of course consume power. This defeats the object so you still need friction brakes or a transmission lock.

Yes, but that's not how it works in real vehicles. Of course shorting a DC motor blocks the shaft (in a lab), but vehicles use 3 phase AC motors and blocking the motor without being able to control the amount of braking, switching the supply source in an emergency situation etc would just never be allowed. By the time you added additional battery backed regulation (for voltage coming from the motors) plus additional control circuitry that would have to be always active, you'd have a system that was heavier, more expensive and less reliable than simply leaving mechanical brakes as a backup and it still would only work if you added a massive dummy load in case the HV battery was fully charged at the time.

McBryce.

Modern EV's don't use "3 phase AC motors". They use brushless DC motors. These brake perfectly well without power They are basically DC permanent magnet motors with no commutator. Yes, most have 3 windings but thy coan have more.  They are not AC induction motors which do need power injection to brake. There may be slight resistance to turning with windings shorted but this is due to residual magentism.